Although various kinds of recording media for recording using an ink jet recording method are commercially available, such as plain paper, coated paper, glossy paper, OHP sheets, back print film, and the like, low-price plain paper is usually used for business applications in a normal office environment. Examples of the required properties in such an environment include alleviation or suppression of a curling (warping or rounding of paper) phenomenon caused when a large amount of ink is provided onto the paper, as well as the satisfaction of ordinary requirements. Herein, it is important to alleviate or suppress curling during recording, as well as curling after recording caused by drying or evaporating of moisture.
Furthermore, as for the formed image, it is also important to suppress the occurrence of an uneven image caused by deformation of the image.
In this regard, as an ink having favorable fixability without image deficiency or unevenness, an ink containing a diglycerin derivative is known (see, for example, Japanese Patent Application Laid-Open No. 10-168373).
Further, as a method for alleviating or suppressing the occurrence of curling, for example, a method for suppressing curls by using a water-based ink containing a solvent having low polarity in an amount of 30% or more with respect to the total mass of the ink is known (see, for example, Japanese Patent Application Laid-Open No. 2007-152873).
Furthermore, as a method for suppressing the clogging of a nozzle, preventing decoloration of a recording solution, and suppressing generation of mold, a water-soluble recording solution for ink jet, containing a water-soluble dye, an alkali silicate as a water-soluble antifungal agent, and water is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2003-165936).
Furthermore, as an ink that exhibits excellent ink ejection, dissolution, and dispersion stability, and thus used in an ink jet printer formed from a film provided with silicone, glass or the like, a water-soluble ink composition having specified pH value and zeta potential is disclosed (see, for example, Japanese Patent Application Laid-Open No. 9-279074).
However, with the ink described in Japanese Patent Application Laid-Open No. 10-168373, occurrence of curling may not be suppressed. In addition, with the ink described in Japanese Patent Application Laid-Open No. 2007-152873, there is a tendency that storage stability of ink or deformation of an image may deteriorate.
Moreover, with the water-soluble recording solution described in Japanese Patent Application Laid-Open No. 2003-165936, occurrence of curling may not be sufficiently suppressed. Further, with the ink described in Japanese Patent Application Laid-Open No. 9-279074, suppression of occurrence of curling and improvement of light resistance may not be sufficient.
In addition, recently, an ink jet recording system has been rapidly distributed due to the advantages that its main body is small and it makes little noise. Examples of the ink jet printer used in the ink jet recording system include those using glass or silicon for a member in view of ease of microfabrication, processing accuracy, processes, or the like.
The ink used in the ink jet printers generally contains a colorant which is dispersed or dissolved in a solvent, a wetting agent, and an aqueous medium. If the ink is filled in an ink jet printer using a member containing glass or silicon as above, and is used or left for a long period of time, the glass or silicon contacting the ink may be eluted. As a result, the design accuracy of the ink jet printer may be lowered, and degradation in the image quality may be caused.
In order to solve these problems, for example, a water-soluble ink composition containing a pigment dispersed by a surfactant, a phosphonium compound, and silicate ions is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2003-165936). Further, an ink composition containing a water-soluble dye and an alkali silicate as a water-soluble antifungal agent is disclosed (see, for example, Japanese Patent Application Laid-Open No. 9-279074).
However, it may be difficult to say that the ink dispersion stability of the water-soluble ink composition described in Japanese Patent Application Laid-Open No. 2003-165936, when a pigment is used particularly as a colorant, is satisfactory in some cases. Further, it may be difficult to say that the light resistance or the water resistance of the water-soluble ink composition described in Japanese Patent Application Laid-Open No. 9-279074 is satisfactory.